The first two rounds in the women's singles saw 459 aces and 687 double faults.

Djokovic, the 2011 champion, saved two set points in the opener before coming through 7-6 (7-2) 6-2 6-2.

"Today was tricky conditions and the first hour I wasn't able to play as well as wanted. After that I felt more confident," said Serb Djokovic, who has reached at least the semi-finals of every Grand Slam event since losing to Jurgen Melzer in the quarter-finals at the 2010 French Open.

His third-round opponent is Portugal's Joao Sousa, who overcame Finn Jarkko Nieminen in a five-set match lasting just short of three hours.

Grandstand

Tommy Haas (Ger) [12] bt Yen-Hsun Lu (Tai) 6-3 6-4 7-6 (7-3)

"It's always about being smart, about how you train and what you do off the court," said the German of still competing at the age of 35. "If your body allows you to do all that stuff, then it's really up to you in many ways."

Hingis and Hantuchova are yet to win two successive matches since teaming up in July

Hingis, who was making a return to Grand Slam tennis as a wildcard after retiring in 2007, double-faulted on the final two points of the match.

The 32-year-old, who has won five Grand Slam singles titles during her career, also lost in the mixed doubles. She and India's Mahesh Bhupathi were beaten 7-6 (7-5) 7-6 (7-5) by Sweden's Robert Lindstedt and Taiwan's Chan Yung-Jan.

"God, give me a break," said the Swiss, when asked if she had considered making a singles comeback after her doubles return.

"No, I haven't given any more thought to it. I have a hard time covering half the court and trying to be there. Full court is completely different ball game."

Quotes of the Day

Laura Robson had a worried look on her face after defeat by Li Na, and it was down to an imminent trip to the dentist to have her wisdom teeth removed. "All the other girls in the locker room are telling me their horror stories," she said. "Oh yeah, I pulled my gauze out and it was just blood. So that's not too nice."

Novak Djokovic has been quizzed as much about his diet as his tennis in week one, and day five was no exception. "The toughest for me [to give up] was definitely chocolate. My father is addicted to chocolate in a way. Was. Not any more. During events I don't have milk chocolate. If I have chocolate I have cacao or dark chocolate - a very little bit."

Li Na is struggling to believe the quality of her own serving, after 11 aces against Laura Robson took her to 21 for the tournament - more than any other woman. "After the match my team said I had over 10, I said 'No like eight or something', my husband said, 'I think even less, maybe six.'"

Sloane Stephens has plenty of confidence off court as well as on. "It's tough to have friends on tour, but I don't lack in the social department. I have some good friends. That's not an area that I struggle in."

"Belgium is a very good team," says Andy Murray when asked to give his opinion about the Scottish football team's next World Cup opponents. "A lot of good, young players. I think they're kind of sort of dark horses for the World Cup. I think they're very, very good. I wouldn't expect Scotland to beat them."

"Everybody has their own issues," says Jamie Hampton when asked about the psychology of tennis. "The girls differ from the guys. Girls are a little bit more emotional. We'll just leave it at that."